Forming apparatus for sheet material

ABSTRACT

A forming apparatus for transforming substantially flat, relatively thin, deformable sheet metal material into narrowly grooved configurations across such sheet material including opposed sets of forming members disposed in elevationally spaced, transversely offset relation with the sheet material lying substantially unrestrained therebetween. Powered actuating devices are utilized for effecting relative movement between the sets of forming members from their elevationally spaced positions to positions disposed in substantially side-by-side elevationally overlapping relation and transversely spaced from each other a distance approximately corresponding to the thickness of the sheet material to permit its substantially unrestricted gathering and flow within the apparatus during formation of the material around the offset forming members to produce corrugations of a depth corresponding to the amount of overlap between the sets of forming members.

United States Patent 91 Miller et al.

[ FORMING APPARATUS FOR SHEET MATERIAL [75] inventors: Kenneth J. Miller, Peoria; Paul H.

Merritt, Morton; Francis W. Fuller, Peoria, all of 111.

[73] Assignee: Caterpillar Tractor Co., Peoria, 111.

[22] Filed: Mar. 4, 1974 [21] Appl. No.: 447,973

[52] US. Cl 72/385; 72/389 [51] Int. Cl 821d 13/02 [58] Field of Search 72/383, 384, 385, 386, 72/389, 307

[56] References Cited UNITED STATES PATENTS 951,630 3/1910 Cooley 72/383 2,290,608 7/1942 Evans 72/385 3,009,510 11/1961 Mcshulam 72/385 3,307,387 3/l967 Lacey et al. 72/385 3,479,855 1 H1969 Ogilvie 72/385 3,511,073 5/1970 Williamson 72/384 3,641,803 2/1972 Schuurbiers et al. 72/385 3,748,889 7/1973 Miller et a1. i 72/385 3,760,624 9/1973 Robinson 72/385 [4 1 July 1,1975

Primary Examiner-C. W. Lanham Assistant Examiner.lames R. Duzan [57] ABSTRACT A forming apparatus for transforming substantially flat, relatively thin, deformable sheet metal material into narrowly grooved configurations across such sheet material including opposed sets of forming members disposed in elevationally spaced, transversely offset relation with the sheet material lying substantially unrestrained therebetween. Powered actuating devices are utilized for effecting relative movement between the sets of forming members from their elevationally spaced positions to positions disposed in substantially side-by-side elevationally overlapping relation and transversely spaced from each other a distance approximately corresponding to the thickness of the sheet material to permit its substantially unrestricted gathering and flow within the apparatus during formation of the material around the offset forming members to'produce corrugations of a depth corresponding to the amount of overlap between the sets of forming members.

10 Claims, 12 Drawing Figures SHEET SHEET FORMING APPARATUS FOR SHEET MATERIAL BACKGROUND OF THE INVENTION This invention relates to an apparatus which is particularly adapted for corrugating relatively thin deformable sheet material for use as the primary surface plates of fixed type heat exchangers or recuperators for gas turbine engines or the like. Corrugated sheet metal material in a range of from two to eight mils in thickness is commonly used to construct the plates of a primary surface recuperator. The sides of the grooves of such corrugated sheet material provide the primary surfaces through which heat is transferred. Consequently, the total surface area provided by such sides, commonly termed fins, determines the heat exchanging capacity of a particular recuperator.

Those skilled in the art will appreciate that the major cost of primary surface recuperators is directly related to the time and labor spent in brazing together selected marginal edges of the numerous primary surface plates utilized therein in order to maintain the separation of the two fluids flowing therethrough during operation. It has long been recognized that such cost could be significantly reduced by decreasing the number of such primary surface plates. However, this alone would result in an undesirable corresponding reduction in the total surface area and heat exchanging capacity of the recuperator.

It is further recognized that the only way to reduce the number of primary surface plates and still maintain the same total surface area is simultaneously to increase the height of the fins and the number of fins per inch. However. this has not heretofore been possible because of the inability of the known prior art forming machines to form the sheet material into corrugations providing more than 25 fins per inch with a tin height greater than 0.04 inch. Typical examples of such prior forming machines are disclosed in U.S. Pat. application Ser. No. 202,948 filed on Nov. 29, l97l, now US. Pat. No. 3,748,889, by Miller et al., and assigned to the assignee of this application; U.S. Pat. Nos. 2,510,024 and 2,954,068; and British Pat. No. 454,229.

OBJECTS OF THE INVENTION An object of this invention is to provide an improved forming apparatus for shaping substantially flat sheet material into a predetermined relatively narrowly grooved corrugated configuration affording a maximum number of grooves or fins per inch.

Another object of this invention is to provide such an improved forming apparatus capable of shaping corrugations in sheet material having a greater depth to width ratio than by any other known method.

Another object of this invention is to provide a forming apparatus of the character described wherein the corrugations in the sheet material are formed individually in a progressively sequential manner to minimize any stretching or tearing of the material.

Other objects and advantages of the present invention will become more readily apparent upon reference to the accompanying drawings and following description.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view ofa forming apparatus embodying the principles of the present invention in association with a pair of reels for dispensing and gathering relatively thin sheet material during operation of the forming apparatus.

FIG. 2 is a rear elevational view of such a forming apparatus as viewed in the direction of the arrows on line Il-ll of FIG. 1.

FIG. 3 is a somewhat enlarged transverse horizontal sectional view through the forming apparatus taken generally along the line III-Ill of FIG. 2.

FIG. 4 is an enlarged vertical sectional view through the forming and clamping shoes of the present invention taken generally along the line lV-IV of FIG. 2.

FIG. 5 is an enlarged fragmentary isometric view illustrating the general construction of one of the clamping shoes.

FIG. 6 is an enlarged fragmentary sectional view taken generally along the lines VIVI of FIG. 3.

FIG. 7 is a greatly enlarged fragmentary sectional view of the forming and clamping members illustrated in FIG. 4 in their fully closed positions.

FIG. 8-11 are fragmentary sectional views similar to FIG. 7, but illustrating the various other sequential positions of the forming and clamping members during operation from their fully open position of FIG. 8 to their nearly fully closed position of FIG. 11.

FIG. 12 is a schematic illustration of a hydraulic and electrical circuit for actuation of the present forming apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring more particularly to the drawings, a forming apparatus embodying the principles of the present invention is generally indicated by the reference numeral 10. Such forming apparatus is utilized for transforming substantially flat, relatively thin sheet metal material, indicated at 11 in FIG. 1, into a corrugated configuration, indicated at 12, by progressive singlefold forming steps which will subsequently be described. In the embodiment disclosed herein, the sheet material is l2 inch wide stainless steel having a thickness of approximately 0.003 inch. Such stainless steel material is commonly commercially available in relatively large rolls, one of which is shown at 14 and rotatably mounted by a free wheeling delivery reel 15 for delivery to the forming apparatus in a generally horizontally disposed plane.

As more clearly shown in FIGS. 1 and 2, the forming apparatus 10 includes a frame assembly 16 having a base 17 upon which is supported a pair of laterally spaced upright side plates 18 and 19. The frame assembly also includes an upper support member 20 extending transversely between and interconnected to the upper ends of the side plates and a lower transversely extending support member 21 which is connected between the side plates adjacent the lower ends thereof.

As more clearly shown in FIGS. 3 and 4, the forming apparatus 10 also includes a pair of elongated opposed upper and lower forming members 23 and 24 which are disposed intermediate the upper and lower support members 20 and 21 of the frame assembly and in longitudinally disposed. transversely extending relation between the side plates 18 and 19. A similar pair of elongated opposed upper and lower clamping members 26 and 27 are disposed in juxtaposed relation to the forming members.

The sheet material 11 is adapted to lie between the upper and lower forming members 23, 24 and the upper and lower clamping members 26, 27 where such sheet material is transformed into its corrugated configuration 12, as will be more fully described in subsequent forming operations.

After transformation. as best shown in FIG. 7, the corrugated material includes a plurality of alternating upwardly and downwardly opening, transversely extending, relatively deep grooves 29 and 30 having relatively closely spaced, substantially vertical sidewalls 31. To accomplish this, the upper forming member 23 and both of the upper and lower clamping members 26 and 27 are provided with relatively thin blades 33, 34 and 35, respectively. Such blades are preferably constructed of hard metal, such as tool steel or the like. The upper forming blade 33, the lower clamping blade 35, and the upper clamping blade 34 are individually disposed generally along vertically disposed parallel planes which are substantially normal to the plane of the sheet material and progressively disposed in spaced offset relation from each other in the direction of material movement through the machine.

Each of such blades is provided with a transversely undulating serpentine profile. as representatively shown by the lower clamping blade 35 in FIG. 5, for purposes which will be described later. The lower clamping blade is secured by press fitting or other acceptable means into a mating serpentine groove 37 formed in a blade holder 38.

The upper forming blade 33 and the upper clamping blade 34 are similarly individually secured in corresponding upper forming and clamping blade holders 40 and 41, respectively. The lower forming member 24 is constructed essentially similar to the forming and clamping blade holders 40, 41 and 38, except that in place of a blade, the lower forming member 24 is provided with an integrally formed, upright sheet material engaging and die forming portion 43. Such die forming portion is provided with an undulating side surface 44 mating with the serpentine profile of the adjacent forming blade 33 and a substantially flat distal end surface 45. The distal end surface and an opposed end surface 47 formed on the upper forming blade holder 40 cooperatively define a sheet material wrinkle ironing device 50 for purposes subsequently to be described.

As best shown in FIG. 4, the upper forming blade holder 40 and the lower forming member 24 are individually mounted on a pair of transversely extending upper and lower forming shoes 52 and 53, respectively. Similarly, the upper and lower clamping blade holders 41 and 38 are mounted on a pair of corresponding upper and lower clamping shoes 55 and 56. As best shown in FIGS. 3 and 4, such blade holders and forming member are secured to their respective shoes by a plurality of bolts 58.

The lower forming shoe 53 is provided with a pair of mounting rings and the lower clamping shoe 56 with a pair of mounting rings 61. Such rings 60, 61 are secured by welding or the like to the opposite left and right hand ends of their respective shoes in juxtaposed relation to their corresponding sidewalls 18, 19 of the frame assembly. Similar pairs of mounting rings 63 and 64 are secured to the upper forming and clamping shoes 52 and 55, but with such rings being transversely inset from the corresponding adjacent rings 60, 61 of the lower shoes 53 and 56. Each of such mounting rings are provided with a counterbored aperture 66 for mounting combined sleeve and thrust bearings 67 therein.

A pair of stepped pivot pins 69 are individually nonrotatably mounted in a pair of aligned aperatures, one of which is shown at 70 in FIG. 3, formed in the side plates 18 and 19 adjacent their front edges. Such pins are received through the bearings 67 of the adjacent set of mounting rings 60, 63 for pivotally mounting the forming shoes 52 and 53 to the frame assembly 16. The inwardly disposed ends of the pivot pins 69 are provided with a pair of spaced upper and lower inwardly protruding ear members 72, 73 and a horizontally axially offset threaded aperture 74.

The clamping shoes 55 and 56 are similarly mounted to the side plates 18 and 19 by a pair of stepped pivot pins 76 which are nonrotatably secured in aligned apertures, one of which is shown at 77, formed adjacent the rear edges of the side plates. The inwardly disposed ends of such pivot pins are provided with a single lower inwardly protruding ear member 79 and a similar h0ri zontally axially offset threaded aperture 80.

The forming and clamping shoes 52, S3, 55 and 56 are individually pivotally actuated by an associated one of a plurality of hydraulic jacks 81, 82, 83 and 84, as best shown in FIG. 1. The rod ends of jacks 81 and 82 are individually pivotally connected to the upper and lower forming shoes 52 and 53 by pins 86 and 87, respectively. The head ends of such jacks are individually pivotally connected to the upper and lower support members 20 and 21 of the frame assembly by pins 88 and 89, respectively. Similarly, pins 90 and 91 pivotally connect the rod ends of the jacks 83 and 84 to the upper and lower clamping shoes 55 and 56, respectively, and pins 92 and 93 pivotally connect the head ends of such jacks to the upper and lower support members, respectively.

A first pair of stop pins 95, FIG. 3, are nonrotatably mounted in a pair of aligned apertures 96 formed through the side plates 18 and 19. Each of such pins extend between a pair of replaaceable cylindrical stop members 98 and 99, as best shown in FIG. 6, which are detachably mounted by countersunk bolts 100 to the opposite ends of the forming shoes 52 and 53, respectively. A second pair of stop pins 102 are nonrotatably mounted in a pair of aligned apertures 103 and extend between a pair of similar replaceable cylindrical stop members 105 and 106 secured to the opposite ends of the clamping shoes 55 and 56. The abutting engagement of the respective stop members against their associated stop pins limits inward pivotal movement of the shoes for controlling the engagement of the forming and clamping members with the sheet material for permitting uniform construction of the corrugations therein. As representatively shown in FIG. 6, each of the inwardly disposed ends of the stop pins 95 and 102 are provided with a horizontally disposed slot 108 for purposes hereinafter described.

The forming apparatus also includes a pair of guide members 110 and 111, which as shown in FIG. 4 are interposed the pairs of forming and clamping shoes, respectively, for guiding and supporting the sheet material to the forming members and the corrugated material away from the clamping members. The guide member 110 includes a pair of vertically spaced, transversely extending plates 113 and 114, each having one of a pair of vertically disposed bars 115, 116 secured to their outer ends. Bolts 117 are disposed through the opposite ends of such bars and screw threadably engaged in the respective ear members 72 and 73 of the pivot pins 69 for securing purposes. The guide mechanism 111 includes a transversely extending. horizontally disposed plate 118 having a vertically disposed bar 119 secured to its outwardly disposed end for mounting the plate to the ear members 79 of the pivot pins 76 by bolts 120. A second plate 122 is secured to the plate 118 in predetermined spaced relation by any suitable means, not shown. As representatively shown in FIG. 6, the adjacent edges of the vertically spaced pairs of plates of the guide members 110 and 111 are received within the slots 108 of the stop pins 95 and 102 for support and alignment purposes.

Two sets of opposed gauge pins 124 and 125, FIG. 3, are individually screw threadably secured in the threaded apertures 74 and 80 of the pivot pins 69 and 76, respectively, for abutting engagement against the opposite lateral edges of the sheet material for maintaining the sheet material in its proper lateral alignment with respect to the forming apparatus during the forming operation. It should be noted that the length of such gauge pins can be varied to accommodate various widths of sheet material other than that shown.

The forming apparatus also includes a feeding mechanism 128, as shown in FIG. 1, for sequentially feeding a predetermined length of sheet material into the forming apparatus at selected intervals during the forming operation. Such feeding mechanism may be of any commercially available structure, such as the Aero- Matic Model 6l3 DFL manufactured by American Monarch Machine Company, Inc. of Peoria, Ill. The feeding mechanism is preferably mounted transversely across the front edges of the side plates 18 and 19 of the forming apparatus by a mounting bracket 129. The feeding mechanism cooperates with a constant tension takeup reel 130 upon which the corrugated material 12 is coiled as it exits from the forming apparatus for sequentially advancing the predetermined length of sheet material into a forming position and for advancing a previously formed length of corrugated material into a clamping position.

As schematically shown in FIG. 12, the hydraulic jacks 81, 82, 83 and 84 are actuated through a hydraulic and electrical control system, generally indicated at 132, for individually pivotally moving the forming members 23 and 24 and the clamping members 26 and 27 between an open position, as best shown in FIG. 8, and a closed position shown in FIG. 7. Such a system includes a hydraulic pump 133 which draws fluid from a tank 134 for supplying pressurized fluid to a plurality of solenoid actuated control valves 135, 136, 137 and 138. A relief valve is provided at 140 to prevent undue proessures from being experienced in the system. The solenoids of such control valves are individually electrically connected to a sequencing mechanism 141. Such sequencing mechanism includes a plurality of switches, one of which is shown at 142, which are actuated by a plurality of cams, one of which is shown at 143. Such cams are mounted on a shaft 144 which is rotatably driven by an electrical motor 146. A source of electrical energy, indicated at 147, is connected through an on-off switch 148 to the motor 146 and the switches 142 of the sequencing mechanism.

The sequencing mechanism 141 is also connected to and includes an appropriate number of switches and cams, not shown, for controlling the feeding mechanism 128 to feed the sheet material into the forming apparatus in proper sequential relation to the forming operation hereinafter described.

OPERATION While the operation of the present invention is believed to be clearly apparent from the foregoing description, further amplification will subsequently be made in the following brief summary of such operation. As indicated earlier, the substantially flat sheet material 11 is drawn from the delivery reel 15 through the forming and clamping members 23, 24, 26 and 27 for transformation into the corrugated material configuration 12. During use, the clamping members clamp and fixedly locate the sheet material while the forming members alternately fold the sheet material in opposite directions to separately form the opposite sidewalls 31 of each of the alternately oppositely opening grooves 29, 30 of the corrugated material. To accomplish this, the hydraulic jacks 81, 82, 83 and 84 and the feeding mechanism 128 are sequentially actuated by the control system 132 through the positions schematically shown in FIGS. 7 through 11.

Upon manual closure of the onoff switch 148, electrical current is directed to the sequencing mechanism 141 and its drive motor 146. When the forming and clamping members are disposed in their open position, as shown in FIG. 8, the sequencing mechanism initially directs electrical current to the solenoid actuating control valve 138. This shifts the valve to direct hydraulic fluid from the pump 133 to the head end of the hydraulic jack 84 to cause the closure of the lower clamping member 27. As shown in FIG. 9, the lower clamping blade 35 of the lower clamping member is positioned ahead of the forward sidewall 31 of the last formed upwardly opening groove 29 of the corrugated material 12. The sequencing mechanism next closes the upper clamping member 26 so that its blade 34 is positioned within the last formed upwardly opening groove so that the material is firmly clamped and properly located between the clamping blades for subsequent forming of the material. It should be recognized that the above closure of the clamping blades 34 and 35 is effective in forming the forward sidewall mentioned above when none exists prior to such closure, as during the forming of the initial fold in the sheet material.

Movement of the upper forming member 23 from its open position shown in FIG. 10 to its closed position shown in FIG. 11 positions its forming blade 33 in overlapping side-by-side relation with the lower clamping blade 35 so as to fold the sheet material about the lower clamping blade which functions as a reaction member during such folding. When the forming blade is in its closed position, the lateral spacing between it and the lower clamping blade 35 is a distance substantially corresponding to the thickness of the sheet material so that the lateral spacing of the sidewalls of the downwardly opening groove formed by such closure is substantially equal to the thickness of the clamping blade 35.

Closure of the lower forming member 24 to the position shown in FIG. 7 is effective to move its die forming portion 43 into engagement with the sheet material to fold it upwardly about the upper forming blade 33 which functions as a reaction member therefor during such folding. Again, the lateral spacing between the side surface 44 of the die forming portion 43 and the upper forming blade 33 is a distance substantially equal to the thickness of the sheet material so that the lateral spacing of the sidewalls of the upwardly opening groove formed thereby is substantially equal to the thickness of the upper forming blade 33. it should be noted that the upper clamping blade 34 is provided with a thickness substantially equal to the forming blade 33 so as to retain the shape of the groove formed by the upper forming blade during engagement of the clamping blade therein for clamping purposes.

In the preferred embodiment, as noted earlier, the forming and clamping members are provided with a transverse serpentine profile so as to form each of the grooves formed thereby with a like transversely undulating serpentine configuration. However, it will be appreciated that due to such serpentine configuration, wrinkles are likely to appear in the unformed sheet material adjacent the previously formed portion thereof. This wrinkling in the past has caused undesirable deformation and tearing of the sheet material during subsequent forming operations. To overcome this problem, such wrinkles are substantially removed or flattened by the close abutting relation between the distal end surface 45 of the die forming portion 43 and the opposed end surface 47 of the upper forming member 23 when in the closed position, as shown in FIG. 7, which is ef fective substantially to remove such wrinkles.

After completing the above forming operation, the control system 132 is effective automatically to reopen the forming and clamping members, as shown in FIG. 8. The feeding mechanism 128, in cooperation with the constant tension takeup reel 130, then advances the unformed sheet material a predetermined distance between the forming members for forming a subsequent groove therein and for advancing the previously formed groove between the clamping members in the manner described above.

The advantages of the corrugated material formed by the heretofore described forming apparatus should be readily apparent to those skilled in the art. Firstly, the sheet material can be formed to provide grooves having a much greater height to width aspect ratio than by prior forming machines. A range of aspect ratios of from 2.5:! to 75:1 is contemplated. In particular, the 0.003 inch thick stainless steel illustrated in the present embodiment is formed so that the grooves are 0,125 inches high, with a center-to-center spacing between adjacent grooves being 0.025 inch, which provides an aspect ratio of 1. Such a center-to-center spacing also provides 40 fins per inch rather than the 25 fins per inch of prior forming machines. Consequently, a recuperator can be constructed with a considerably fewer number of primary surface plates made from the present corrugated material so as to greatly reduce the overall cost of the recuperator.

Without the transversely undulating serpentine profile, much greater aspect ratios would be attainable. However, such serpentine profile is highly advantageous because of its ability to break up the thermal boundary layers frequently formed in the fluids flowing through such recuperator in operation so as to yield higher heat transfer conductances than possible with straight grooves.

in addition to the attainment of the high aspect ratio and the serpentine profile with the structure of the present invention, another advantage is its ability to form the sheet material so that the grooves opening on one side thereof are provided with a relatively greater cross sectional area than the grooves opening on the opposite side. This is accomplished by utilizing different thickness blades on the opposite sides of the material. ln particular, the upper forming and clamping blades 33 and 34, respectively, are provided with a thickness of 0.023 inch, whereas the lower clamping blade 35 is provided with a thickness of 0.0l l inch. Because of the side-by-side spacing of such blades, as noted earlier, which forms the width of the grooves substantially equal to the thickness of the blades, the upwardly opening grooves are provided with approximately twice the cross sectional area as the downwardly opening grooves. Such a two-to-one difference in cross sectional area is particularly advantageous in recuperators for gas turbine engines so that the mass flow of the hot exhaust gases can be more evenly matched with mass flow of the denser intake air in order to reduce overall pressure losses of such recuperators.

While the invention has been described and shown with particular reference to the preferred embodiment, it will be apparent that variations might be possible that would fall within the scope of the present invention, which is not intended to be limited except as defined in the following claims.

What is claimed is:

l. A forming apparatus for transforming substantially flat, relatively thin deformable metal sheet material into narrowly grooved corrugations across such material, comprising:

means for feeding said sheet material along a predetermined path from an inlet to an outlet;

opposed first and second clamping members spaced on opposite sides of the path;

means for selectively moving said clamping members into engagement against opposite sides of the sheet material for clamping the material therebetween with said second clamping member defining a reaction member in abutting engagement against one side of the material and having an inlet-facing side generally normal to said path;

opposed first and second forming members spaced on opposite sides of said path in juxtaposition to their corresponding first and second clamping members and on the inlet side thereof, said first forming member including a relatively thin forming blade having opposite inlet and outlet sides, said second forming member being on the same side of the sheet material as the reaction member and including a die forming portion having an outletfacing side facing the inlet-facing side of the reaction member and in predetermined laterally spaced relation thereto, and said forming blade being spaced intermediate the outlet-facing side of the die forming portion and the inlet-facing side of the reaction member in offsetting relation on the opposite side of the sheet material;

means for mounting each of the forming members for limited pivotal movement about an axis spaced a predetermined distance from their respective forming blade and die forming portion in a direction toward the inlet;

first means for moving the first forming member about its axis so that its forming blade is moved through an arc between a first position in which it is spaced from the sheet material and a second position in which it is in substantially parallel, closely spaced side-by-side relation with the inlet-facing side of the reaction member;

second means for moving said second forming member about its axis so that its die forming portion is moved through a similar arc between a first position in which it is spaced from the sheet material and a second position in which its outlet-facing side is in substantially parallel, closely spaced side-byside relation with the adjacent side of the forming blade; and

means for sequentially operating said first and second means so that said sheet material is first folded in one direction about said reaction member by said forming blade and is subsequently folded in an opposite direction about said forming blade by said die forming portion so as to sequentially form the opposite sidewalls of said corrugations as the sheet material is fed through the apparatus.

2. A forming apparatus of claim 1 wherein the corrugations formed in the sheet material define a plurality of alternately opening grooves having opposite sidewalls common with their adjacent grooves and includmg;

first and second relatively thin clamping blades individually provided on said first and second clamping members; and

means for mounting each of the clamping members for limited pivotal movement about an axis spaced a predetermined distance toward the outlet from each of the clamping blades so that the first clampin g blade is moved in an arc between a first position in which it is spaced from the sheet material and a second position in which it is received in the last full groove formed by the apparatus, and the second clamping blade is moved in a similar arc between a first material spaced position and a second position in which it is disposed in closely spaced sideby-side relation on the inlet side of the first clamping blade with the last formed sidewall of the last groove being disposed in supported relation therebetween and with the second clamping blade defining said reaction member.

3. The forming apparatus of claim 2 wherein each of the preceding closely spaced side-by-side relations approximate the thickness of the sheet material so that the grooves formed about the second clamping blade have their opposite sidewalls spaced a distance substantially equal to the thickness of such clamping blade and the opposite opening groove formed about the forming 10 blade have their sidewalls spaced a distance substantially equal to the thickness of such forming blade.

4. The forming apparatus of claim 3 wherein said forming blade and said second clamping blade are provided with a predetermined material penetrating height which is substantially greater than their thicknesses so that the grooves formed thereby have a depth which is greater than 2.5 times the lateral center to center spacing between adjacent grooves.

5. The forming apparatus of claim 4 wherein one of the forming blade and the second clamping blade is provided with a thickness substantially greater than the other so that the distance between the sidewalls of the grooves opening on one side of the sheet material is approximately twice the distance between the sidewalls of the grooves opening on the other side thereof to provide a 2 to 1 area differential between such grooves.

6. The forming apparatus of claim 5 wherein the outlet side of the die forming portion and the opposite side of the clamping and forming blades are provided with mating serpentine profiles to form said grooves with a transversely undulating serpentine configuration.

7. The forming apparatus of claim 6 including sheet material ironing means provided on the forming members for substantially removing any wrinkles appearing in the sheet material adjacent the corrugations formed by the forming members to prevent undesirable deformation and tearing of the sheet material during subsequent forming operations.

8. The forming apparatus ofclaim 7 including control system means for operatively controlling said first and second means for moving said first and second forming members, said means for moving said clamping members, and said feeding means in a predetermined sequential manner to provide continuous progressive corrugating of the sheet material.

9. The forming apparatus of claim 8 including guide means disposed in abutting relation with the opposite lateral edges of the sheet material for maintaining the sheet material in proper alignment with said forming and clamping members during corrugating to assist in the uniform construction of corrugations formed by the apparatus.

10. The forming apparatus of claim 9 including stop means for limiting the pivotal movement of said forming and clamping members towards the sheet material to insure the forming of the grooves to a uniform depth. F l i 

1. A forming apparatus for transforming substantially flat, relatively thin deformable metal sheet material into narrowly grooved corrugations across such material, comprising: means for feeding said sheet material along a predetermined path from an inlet to an outlet; opposed first and second clamping members spaced on opposite sides of the path; means for selectively moving said clamping members into engagement against opposite sides of the sheet material for clamping the material therebetween with said second clamping member defining a reaction member in abutting engagement against one side of the material and having an inlet-facing side generally normal to said path; opposed first and second forming members spaced on opposite sides of said path in juxtaposition to their corresponding first and second clamping members and on the inlet side thereof, said first forming member including a relatively thin forming blade having opposite inlet and outlet sides, said second forming member being on the same side of the sheet material as the reacTion member and including a die forming portion having an outlet-facing side facing the inlet-facing side of the reaction member and in predetermined laterally spaced relation thereto, and said forming blade being spaced intermediate the outlet-facing side of the die forming portion and the inlet-facing side of the reaction member in offsetting relation on the opposite side of the sheet material; means for mounting each of the forming members for limited pivotal movement about an axis spaced a predetermined distance from their respective forming blade and die forming portion in a direction toward the inlet; first means for moving the first forming member about its axis so that its forming blade is moved through an arc between a first position in which it is spaced from the sheet material and a second position in which it is in substantially parallel, closely spaced side-by-side relation with the inlet-facing side of the reaction member; second means for moving said second forming member about its axis so that its die forming portion is moved through a similar arc between a first position in which it is spaced from the sheet material and a second position in which its outlet-facing side is in substantially parallel, closely spaced side-by-side relation with the adjacent side of the forming blade; and means for sequentially operating said first and second means so that said sheet material is first folded in one direction about said reaction member by said forming blade and is subsequently folded in an opposite direction about said forming blade by said die forming portion so as to sequentially form the opposite sidewalls of said corrugations as the sheet material is fed through the apparatus.
 2. A forming apparatus of claim 1 wherein the corrugations formed in the sheet material define a plurality of alternately opening grooves having opposite sidewalls common with their adjacent grooves and including; first and second relatively thin clamping blades individually provided on said first and second clamping members; and means for mounting each of the clamping members for limited pivotal movement about an axis spaced a predetermined distance toward the outlet from each of the clamping blades so that the first clamping blade is moved in an arc between a first position in which it is spaced from the sheet material and a second position in which it is received in the last full groove formed by the apparatus, and the second clamping blade is moved in a similar arc between a first material spaced position and a second position in which it is disposed in closely spaced side-by-side relation on the inlet side of the first clamping blade with the last formed sidewall of the last groove being disposed in supported relation therebetween and with the second clamping blade defining said reaction member.
 3. The forming apparatus of claim 2 wherein each of the preceding closely spaced side-by-side relations approximate the thickness of the sheet material so that the grooves formed about the second clamping blade have their opposite sidewalls spaced a distance substantially equal to the thickness of such clamping blade and the opposite opening groove formed about the forming blade have their sidewalls spaced a distance substantially equal to the thickness of such forming blade.
 4. The forming apparatus of claim 3 wherein said forming blade and said second clamping blade are provided with a predetermined material penetrating height which is substantially greater than their thicknesses so that the grooves formed thereby have a depth which is greater than 2.5 times the lateral center to center spacing between adjacent grooves.
 5. The forming apparatus of claim 4 wherein one of the forming blade and the second clamping blade is provided with a thickness substantially greater than the other so that the distance between the sidewalls of the grooves opening on one side of the sheet material is approximately twice the distance between the sidewalls of thE grooves opening on the other side thereof to provide a 2 to 1 area differential between such grooves.
 6. The forming apparatus of claim 5 wherein the outlet side of the die forming portion and the opposite side of the clamping and forming blades are provided with mating serpentine profiles to form said grooves with a transversely undulating serpentine configuration.
 7. The forming apparatus of claim 6 including sheet material ironing means provided on the forming members for substantially removing any wrinkles appearing in the sheet material adjacent the corrugations formed by the forming members to prevent undesirable deformation and tearing of the sheet material during subsequent forming operations.
 8. The forming apparatus of claim 7 including control system means for operatively controlling said first and second means for moving said first and second forming members, said means for moving said clamping members, and said feeding means in a predetermined sequential manner to provide continuous progressive corrugating of the sheet material.
 9. The forming apparatus of claim 8 including guide means disposed in abutting relation with the opposite lateral edges of the sheet material for maintaining the sheet material in proper alignment with said forming and clamping members during corrugating to assist in the uniform construction of corrugations formed by the apparatus.
 10. The forming apparatus of claim 9 including stop means for limiting the pivotal movement of said forming and clamping members towards the sheet material to insure the forming of the grooves to a uniform depth. 